Continuous wave (CW) radar system for phase-coded time delayed transmit-receive leakage cancellation

ABSTRACT

Disclosed is a method, system, and apparatus for transmitting a randomly phase-coded CW waveform in a manner that suppresses signal leakage and enables the recovery of polyphase subcodes advantageous for the purposes of correlation and pulse compression. The CW system transmits and receives a random waveform while concurrently providing properly delayed phase conversion parameters (ϕ i −Θ i ) from a corrections generator to various range gates. Each range gate processes any echo returns using a most recent phase conversion parameters (ϕ k −Θ k ) provided and correlation of the resulting echo subcodes ϕ R  produce either target indications or noise signals, depending on the most recent phase conversion parameters (ϕ k −Θ k ) provided to the range gate. The system may transmit the randomly phase-coded CW waveform while recovering any phase code {ϕ 1 , ϕ 2 , . . . ϕ N } that lends itself to advantageous pulse compressions.

RELATION TO OTHER APPLICATIONS

This patent application claims the benefit of U.S. ProvisionalApplication No. 62/479,381 filed Mar. 31, 2016, which is herebyincorporated in its entirety.

FIELD OF THE INVENTION

One or more embodiments relates generally to a randomly phase-codedcontinuous wave (CW) radar system.

BACKGROUND

Random signal radars are radars whose transmitting signal is typicallymodulated by some noise source in order to generate a randomtransmitting signal. Because of the random properties of the signal,these radars have multiple advantages compared with conventional radars,including unambiguous measurement of range and Doppler estimations, highimmunity to noise, lower detection probabilities, and advantageousambiguity functions, among others.

For most applications, the random signal is either transmitted directlyfrom the noise-generating source or generated digitally, then convertedto analog and upconverted to carrier level. Correlation of the echoreturns uses the principle that when the delayed replica of thetransmitted signal is correlated with the actual target echo, the peakvalue of the correlation process can indicate the distance to thetarget. The replica of the transmitted noise, delayed, is correlatedwith a received signal, and strong correlation peaks are utilized toprovide round trip time (RTT) estimations and ranging. This methodologygenerally requires a significant amount of processing and computationalresources at both the transmitting and receiving ends of the system, andchallenges abound. Additionally, because correlations are conductedusing the delayed replica of the random transmission as a template, anyability to utilize specific phase codes more amenable to advantageousphase compressions is generally sacrificed.

Additionally in CW systems random or otherwise, leakage from atransmitted signal generally occurs due to circuit leakages, free spacepropagation, near field coupling, or other propagation modes. Thedetails depend on the specific system architecture and whether single ormultiple antennas are used. For close in targets, the leakage signalstrength s_(l)(t) is generally much smaller than the signal strengthreturned to the radar from the target, however at longer ranges or forlow radar cross section targets, the received signal from the targets_(t)(t) is very weak. Since the receiver must operate when transmissionis occurring, the leakage signal can still be much larger than thetarget return. In the absence of close-in clutter the leakage can bereduced by increasing the antenna spacing, but there is a practicallimit to this. In the actual construction and operation of a radarsystem it is impossible to achieve zero leakage. Thus the isolationbetween the transmitting and receiving antennas (or channels) is oftenone of the limiting factors in the performance of CW radars.

It would be advantageous to provide a CW radar system which employs arandomly phase-coded system in order to realize the associatedadvantages while also providing the ability to recover specific phasecodings more amenable to advantageous phase compressions. It would beadditionally advantageous if the CW system eliminated some portion ofthe significant processing and computational resources associated withdelayed replica correlation. It would provide additional advantage issuch a system could transmit continuous wave signal in a manner greatlymitigating the impact of signal leakage.

These and other objects, aspects, and advantages of the presentdisclosure will become better understood with reference to theaccompanying description and claims.

SUMMARY

A particular embodiment of the Continuous Wave (CW) Radar Systemcomprises a random waveform generator providing a plurality of randomsubcodes Θ_(i). The random waveform generator communicates the randomsubcodes Θ_(i) to a modulator, which upconverts the random subcode Θ_(i)to a modulated subcode Θ′_(i) for subsequent transmission. The modulatedsubcode Θ′_(i) generated is an electromagnetic signal having a frequencyand a phase over a subpulse width τ, where the frequency is typicallyfixed and the phase is dependent on the most recent random subcode Θ_(i)received. The modulator communicates the modulated subcode Θ′_(i) to atransmitting antenna as well as to a corrections generator.

In conjunction, a polyphase subcode generator produces a polyphasesubcode ϕ_(i) corresponding to each random subcode Θ_(i). The polyphasesubcode ϕ_(i) is a member of a set of polyphase subcodes having at leastN number of members. For example, the polyphase subcode ϕ_(i) may be amember of a set defining one of the code sequences known as Barker,Frank, Chu, Milewski, and others, however this is not required, and thepolyphase subcode ϕ_(i) may be a member of any set defining anyphase-coding scheme. The polyphase subcode generator additionallycommunicates the polyphase subcode ϕ_(i) to the corrections generator.The corrections generator is further in data communication with aplurality of range gates RG_(j), where j is used to denote a countinginteger greater than or equal to 1 and less than some maximum integer m.Each range gate RG_(j) provides range binning for a range interval ofthe CW system.

Generally for each subpulse width τ, the corrections generator generatesa phase conversion parameter (ϕ_(i)−Θ_(i)) using the subcode Θ_(i) andthe corresponding polyphase subcode ϕ_(i) received. The correctionsgenerator subsequently provides the phase conversion parameter(ϕ_(i)−Θ_(i)) generated for the random subcode Θ_(i) to each individualrange gate RG_(j) using a delay D_(j) specific and unique to thatparticular range gate. In a typical embodiment, each individual rangegate RG_(j) has an associated delay generally dependent on a time equalto (τ×j)+ΔT_(P(j)), where j corresponds to the indexing integer of therange gate, (τ×j) indicates the subpulse width τ multiplied by theindexing integer of the range gate RG_(j), and ΔT_((j)) is a processingtime required by receiving components in the system. Under thisarrangement, each range gate RG_(j) generally receives a new phaseconversion parameter (ϕ_(i)−Θ_(i)) corresponding to each subpulse widthτ of the modulated subcode Θ′_(i) transmitted. However, because of thedelay D of (τ×j)+ΔT_(P(j)) applicable to each range gate RG_(j), thephase conversion parameter most recently received at a given range gatefrom corrections generator varies among the range gates. As a result,each range gate RG_(j) has a most recent phase conversion parameter(ϕ_(k)−Θ_(k)) received from the corrections generator.

The CW system receives and processes echoes by receiving a modulatedecho Θ′_(R) and demodulating the echo to generate a demodulated subcodeΘ_(R). The demodulated subcode Θ_(R) is provided to each range gateRG_(j), which converts the phase of the demodulated subcode Θ_(R) usingits most recent phase conversion parameter (ϕ_(k)−Θ_(k)). The range gateRG_(j) adds the resulting echo subcode ϕ_(R) to a string of subcodes andthen correlates the updated polyphase sequence against the set of Npolyphase subcodes utilized by the polyphase subcode generator. As aresult of the associated time delays generating different (ϕ_(k)−Θ_(k))parameters to each range gate, and the random nature of the modulatedsubcode Θ′_(i) being transmitted, and the demodulated subcode Θ_(R)being supplied, the resulting phase conversion and correlation at eachrange gate substantially generates either a compressed {ϕ₁, ϕ₂, . . .ϕ_(N)} pulse when the echo originates within the range intervalcorresponding to the range gate RG_(j), or substantially generates anoise signal otherwise. Subsequent integration is typically utilized toidentify the range interval from which a given modulated echo Θ′_(R)originated.

The novel apparatus and principles of operation are further discussed inthe following description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an embodiment of the CW system.

FIG. 2 illustrates a specific embodiment of a range gate.

FIG. 3 illustrates a plurality of random phase subcodes.

FIG. 4 illustrates a modulated randomly phase-coded waveform.

FIG. 5 illustrates a plurality of polyphase subcodes.

FIG. 6 illustrates another embodiment of the CW system.

FIG. 7 illustrates exemplary parameters utilized by the CW system.

FIG. 8 illustrates delayed phase conversion parameters (ϕ_(i)−Θ_(i))provided to a plurality of range gates.

FIG. 9 illustrates a response of the plurality of range gates to echoreturns from a first object.

FIG. 10 illustrates a response of the plurality of range gates to echoreturns from a second object.

FIG. 11 illustrates a response of the plurality of range gates to echoreturns from multiple objects.

FIG. 12 illustrates a response of the plurality of range gates to echoreturns from an objects in the presence of signal leakage.

Embodiments in accordance with the invention are further describedherein with reference to the drawings.

DETAILED DESCRIPTION OF THE INVENTION

The following description is provided to enable any person skilled inthe art to use the invention and sets forth the best mode contemplatedby the inventor for carrying out the invention. Various modifications,however, will remain readily apparent to those skilled in the art, sincethe principles of the present invention are defined herein specificallyto provide a method, system, and apparatus for transmission of a randomphase-coded waveform while providing for recovery of an underlying phasecode.

Provided here is a method, system, and apparatus for transmitting arandomly phase-coded CW waveform in a manner enabling the recovery ofpolyphase subcodes advantageous for the purposes of correlation andpulse compression. The CW system disclosed transmits and receives arandom phase-coded waveform while concurrently providing properlydelayed phase conversion parameters (ϕ_(i)−Θ_(i)) from a correctionsgenerator to each of a plurality of range gates RG_(j). Each range gateidentifies and processes any echo returns using a most recent phaseconversion parameters (ϕ_(k)−Θ_(k)) provided from the correctionsgenerator, and correlation of the resulting echo subcodes ϕ_(R) produceeither target indications or noise signals, depending on the most recentphase conversion parameters (ϕ_(k)−Θ_(k)) provided to the range gate.The method, system, and apparatus provided differs substantially fromthat employed by typical random radars transmitting randomly phase codedCW waveforms, which typically rely on recording and updating a series ofecho subcodes received for subsequent comparison against a delayedreplica, in order to determine round trip time (RTT) and provide rangingfunctionality. Additionally, in typical random radars, the randomtransmitted waveform is typically correlated against the (also random)delayed replica, and any ability to utilize specifically advantageousphase codes is lost. In contrast, the system, method, and apparatusdisclosed here provides for transmission of a random CW waveform whilealso allowing the use of any phase code {ϕ₁, ϕ₂, . . . ϕ_(N)} that lendsitself to advantageous pulse compressions.

A particular embodiment of the Continuous Wave (CW) Radar Systemdisclosed is illustrated at FIG. 1. At FIG. 1, CW System 100 comprisesrandom waveform generator 101 typically comprising a noise source 102.Random waveform generator 101 generates a random phase coded waveformbased on noise source 102, where the random phase coded waveformcomprises a plurality of random subcodes Θ_(i) with each random subcodeΘ_(i) corresponding to a subpulse width τ, where τ is a measure of time.The random waveform generator 101 communicates the random subcode Θ_(i)to a modulator 103 which receives each random subcode Θ_(i) andupconverts the random subcode Θ_(i) to a modulated subcode Θ′_(i). Insome embodiments modulator 103 comprises a digital processor andprovides a digital-to-analog conversion of the random subcode Θ_(i) inorder to upconvert to the modulated subcode Θ′_(i). Such digitalmodulation methods are known in the art. The modulated subcode Θ′_(i)generated is an electromagnetic signal having a frequency and a phaseover the subpulse width τ, where the frequency is typically fixed andthe phase is dependent on the random subcode Θ_(i) corresponding to asubpulse width τ. In particular embodiments, this is the most recentrandom subcode Θ_(i) received by Modulator 103. The modulatorcommunicates the modulated subcode Θ′_(i) to a transmitting antenna 104,which transmits the modulated subcode Θ′_(i) at a time t_(i) for aperiod of time equivalent to the subpulse width τ. Random waveformgenerator 101 additionally communicates each random subcode Θ_(i) tocorrections generator 106 via, for example, 107.

In conjunction, a polyphase subcode generator 105 produces a polyphasesubcode corresponding to each random subcode Θ_(i). The polyphasesubcode ϕ_(i) is a member of a set of polyphase subcodes having N numberof members. For example, the polyphase subcode ϕ_(i) may be a member ofa set defining one of the code sequences known as Barker, Frank, Chu,Milewski, and others, however this is not required. Within thisdisclosure, the polyphase subcode ϕ_(i) may be a member of any setdefining any phase-coding scheme. Polyphase subcode generator 105additionally communicates the polyphase subcode ϕ_(i) to correctionsgenerator 106, as illustrated.

Corrections generator 106 is in data communication with a plurality ofrange gates RG_(j), where j is used to denote a counting integer greaterthan or equal to 1 and less than some maximum integer m, where m>1. Forexample at FIG. 1, the plurality of range gates RG_(j) comprises RG₁,RG₂, RG₃, and so on to the range gate indicated as RG_(m). Each rangegate RG_(j) generally corresponds to a range bin dependent on thesubpulse width τ utilized, as is typical for CW radars. For example atFIG. 1, range gate RG₁ provides binning for the range interval generallyindicated by RH₁, range gate RG₂ provides binning for the range intervalgenerally indicated by RH₂, range gate RG₃ provides binning for therange interval generally indicated by RH₃, and range gate RG_(m)provides binning for the range interval generally indicated by RH_(m).In typical embodiments, each range interval generally covers a physicaldisplacement equal to about τs/2, where c is the speed of light. Asindicated at FIG. 1 and as will be discussed later, in typicalembodiments there is no RG_(j) range gate intended to provide binningfor the range interval RH₀ in order to enhance leakage suppression.

As discussed, for each subpulse width τ associated with a random subcodeΘ_(i), corrections generator 106 receives both the random subcode Θ_(i)generated by random waveform generator 101 and the polyphase subcodeϕ_(i) generated by polyphase subcode generator 105. Correctionsgenerator 106 then generates a phase conversion parameter (ϕ_(i)−Θ_(i))using the subcode Θ_(i) and the corresponding polyphase subcode ϕ_(i).Corrections generator 106 subsequently provides the phase conversionparameter (ϕ_(i)−Θ_(i)) generated for the random subcode Θ_(i) andcorresponding polyphase subcode ϕ_(i) to each individual range gateRG_(j) using a delay D_(j) specific and unique to that particular rangegate, where the delay D_(j) follows the time t, when transmittingantenna 104 transmits the modulated subcode Θ′_(i) derived from therandom subcode Θ_(i). These delays are represented at FIG. 1 by theseries of delays illustrated as D₁, D₂, D₃, and D_(m). In a typicalembodiment the individual delays D_(j) are representative of timeperiods defined generally by (τ×j)+ΔT_(P(j)), where τ is the subpulsewidth τ and ΔT_(P(j)) is typically a time period required in order toreceive and process an echo to a form suitable for delivery to theplurality of range gates RG_(j), as will be discussed. The ΔT_(P(j)) maybe a period specific and known by CW system 100 for each range gateRG_(j) based on timing diagnostics or other testing, or in someembodiments may be a period common to all range gates RG_(j) in theplurality. However, the individual delays D_(j) need not adhere orstrictly depend on the exemplary (τ×j)+ΔT_(P(j)) expression, providedthe individual delays D_(j) are specific and unique to a range gateRH_(j). In some embodiments, a timing circuit 110 is in communicationwith at least random waveform generator 101, polyphase subcode generator105, and corrections generator 106, in order to provide timing signalsfor appropriate random subcode Θ_(i) and polyphase subcode ϕ_(i)delivery, association for generating the phase conversion parameter(ϕ_(i)−Θ_(i)), and to provide timing or other signals by which a givenphase conversion parameter (ϕ_(i)−Θ_(i)) is provided to a given rangegate RG_(j) based on an appropriate delay D_(j), among othersynchronizations that may be necessary.

The phase conversion parameter (ϕ_(i)−Θ_(i)) is generated by correctionsgenerator 106 using an operation such as a digital process, an analogprocess, or some combination therein. The phase conversion parameter(ϕ_(i)−Θ_(i)) generated by the digital process, the analog process, orthe combination can be used in conjunction with a given random subcodeΘ_(i) to substantially produce the polyphase subcode ϕ_(i) produced bypolyphase generator 105 which corresponds to the given random subcodeΘ_(i). As previously mentioned, polyphase subcode generator 105 producesa polyphase subcode ϕ_(i) corresponding to each random subcode Θ_(i)generated by random waveform generator 101 for each subpulse width τ,and corrections generator 106 then generates a phase conversionparameter (ϕ_(i)−Θ_(i)) using the subcode Θ_(i) and the correspondingpolyphase subcode ϕ_(i), such that for a specific random subcodeΘ_(i(S)) and a corresponding specific polyphase subcode ϕ_(i(S)),corrections generator 106 generates a specific phase conversionparameter (ϕ_(i(S))−Θ_(i(S))). Given the random nature of the randomsubcodes Θ_(i) generated by random waveform generator 101, in order tosubstantially produce the specific polyphase subcode ϕ_(i(S))corresponding to the specific random subcode Θ_(i(S)) using a phaseconversion parameter, both the specific phase conversion parameter(ϕ_(i(S))−Θ_(i(S))) generated for the specific random subcode Θ_(i(S))and an approximate version or replica of the specific random subcodeΘ_(i(S)) must be present, as discussed further below.

Under this arrangement, each range gate RG_(j) generally receives a newphase conversion parameter (ϕ_(i)−Θ_(i)) corresponding to each subpulsewidth τ of the modulated subcode Θ′_(i) transmitted by transmittingantenna 104. However, because of the delay D of, for example,(τ×j)+ΔT_(P(j)) applicable to each range gate RG_(j), the phaseconversion parameter most recently received at a given range gate fromcorrections generator 106 varies among the range gates. As a result,each range gate RG_(j) has a most recent phase conversion parameter(ϕ_(k)−Θ_(k)) received from corrections generator 106, where the(ϕ_(k)−Θ_(k)) received is a properly delayed phase conversion parameter(ϕ_(i)−Θ_(i)), and where generally at any given instant, the most recentphase conversion parameter (ϕ_(k)−Θ_(k)) for a specific range gateRG_(j) is unique to the specific range gate RG_(j) in the plurality ofrange gates RG_(j). For example at FIG. 1, the most recent phaseconversion parameter (ϕ_(k)−Θ_(k)) for RG₁ is (ϕ_(k(1))−Θ_(k(1))), themost recent phase conversion parameter (ϕ_(k)−Θ_(k)) for RG₂ is(ϕ_(k(2))−Θ_(k(2))), and the most recent phase conversion parameter(ϕ_(k)−Θ_(k)) for RG₃ is (ϕ_(k(3))−Θ_(k(3))), with typically(ϕ_(k(1))−Θ_(k(1))), (ϕ_(k(2))−Θ_(k(2))), and (ϕ_(k(3))−Θ_(k(3)))representing non-equivalent signals due at least to the random nature ofthe random subcodes Θ_(k(1)), Θ_(k(2)), and Θ_(k(3)) on which therespective most recent phase parameters are based, as well as therespective polyphase subcodes ϕ_(k(1)), ϕ_(k(2)), and ϕ_(k(3)) whichtypically vary from a first subpulse width τ to a subsequent subpulsewidth τ.

CW system 100 performs the steps described on a cyclic basis, in orderto transmit a continuous wave random radar signal comprising a pluralityof modulated subcodes Θ′_(i) and, for each modulated subcode Θ′_(i),provide phase conversion parameters (ϕ_(i)−Θ_(i)) to each range gateRG_(j), where the phase conversion parameter (ϕ_(i)−Θ_(i)) comprises apolyphase subcode ϕ_(i) corresponding to one of the transmittedmodulated subcodes Θ′_(i), and where the polyphase subcode ϕ_(i) is amember of a set of polyphase subcodes having at least N number ofmembers. Each of the range gates RG_(j), utilizes the phase conversionparameters (ϕ_(i)−Θ_(i)) received in order to process a received echo,as discussed below.

CW system 100 receives and processes echoes by receiving a modulatedecho Θ′_(R) through antenna 108 and communicating the modulated echoΘ′_(R) to demodulator 109, which demodulates the echo, generates ademodulated subcode Θ_(R), and provides the demodulated subcode Θ_(R) toeach range gate RG_(j) over the processing time ΔT_(P(j)). Theprocessing period ΔT_(P(j)) is generally the period from receipt of anecho at a receiving antenna such as antenna 108 through supply of thedemodulated subcode Θ_(R) to a specific range gates RG_(j), and asdiscussed may be a time period common to all range gates RG_(j). Incertain embodiments, the ΔT_(P(j)) is used to determine a delay D_(j) of(τ×j)+ΔT_(P(j)) observed by corrections generator 106. For a given CWsystem 100, the processing periods ΔT_(P(j)) with respect to a givendemodulator 109 and a given range gate RG_(j) may be determined for agiven collection of hardware components. In typical embodiments, timingcircuit 110 is further in communication with demodulator 109 to providetiming signals for coordination among at least random waveform generator101, polyphase subcode generator 105, and corrections generator 106. Inparticular embodiments demodulator 109 comprises a digital processor andprovides an analog-to-digital conversion of the modulated echo Θ′_(R) inorder to demodulate the echo to the demodulated subcode Θ_(R). Suchdigital demodulation methods are known in the art.

Having received the demodulated subcode Θ_(R) from demodulator 109, eachrange gate RG_(j) converts the phase of the demodulated subcode Θ_(R)using its most recent phase conversion parameter (ϕ_(k)−Θ_(k)) receivedfrom corrections generator 106 and generates an echo subcode ϕ_(R). Therange gate RG_(j) adds the resulting echo subcode ϕ_(R) to a string ofsubcodes comprising echo subcodes previously received to generate anupdated polyphase sequence, and then correlates the updated polyphasesequence using a matched filter, where in an embodiment the matchedfilter utilizes a reference register comprising the set of N polyphasesubcodes utilized by polyphase subcode generator 106. As a result of theassociated time delays generating different (ϕ_(k)−Θ_(k)) parameters toeach range gate, and the random nature of the modulated subcode Θ′_(i)being transmitted and the demodulated subcode Θ_(R) being supplied, as agiven range gate phase rotates or converts the demodulated subcode Θ_(R)for a given subpulse width τ to generate the updated polyphase sequence,the correlation of the updated polyphase sequence will generate acompressed {ϕ₁, ϕ₂, . . . ϕ_(N)} pulse only when the delayed(ϕ_(k)−Θ_(k)) parameter matches an echo originating within the rangeinterval corresponding to the range gate RG_(j), and substantiallygenerate a noise signal otherwise. Subsequent integration of the outputof each matched filter within the plurality of range gates RG_(j) issubsequently utilized to identify the range interval from which a givenmodulated echo Θ′_(R) originated.

This methodology differs substantially from that employed by typicalrandom radars transmitting randomly phase coded CW waveforms. In atypical random radar, following receipt of an echo analogous tomodulated echo Θ′_(R), the random radar records and updates a series ofecho subcodes received, then compares the resulting string of subcodesto a delayed replica of previously transmitted subcodes in order todetermine a round trip time (RTT), based on when the delayed replica wasoriginally transmitted. The correct range gate is then generallyactivated based on the RTT resulting from this direct comparison of thereceived and replicated strings of subcodes. Further, any pulsecompression which is performed is conducted using a matched filterhaving some version of the delayed replica as a template. Because thetransmitted waveform is necessarily random and the delayed replica issubsequently also random, this eliminates any ability to generate phasecodes which may be more amenable to phase compression, such as theaforementioned Barker, Frank, Chu, Milewski, and other phase codeschemes. In contrast, CW system 100 of FIG. 1 transmits and receives arandom waveform while avoiding the necessary use of a delayed replicafor RTT determination, by providing properly delayed phase conversionparameters (ϕ_(i)−Θ_(i)) from corrections generator 106 to the variousrange gates RG_(j). In addition to avoiding the additional processingassociated with the necessary storing and subsequent comparison againsta delayed replica as performed in current random radars, the methodologyof CW system 100 also has the significant advantage of enabling recoveryof the underlying phase code {ϕ₁, ϕ₂, . . . ϕ_(N)} associated with agiven {Θ₁, Θ₂, . . . Θ_(N)} series of modulated subcodes Θ′_(i)transmitted, based on the phase conversion parameters (ϕ_(i)−Θ_(i))appropriately delayed and provided by corrections generator 106. Thisallows use of any phase code {ϕ₁, ϕ₂, . . . ϕ_(N)} that lends itself toadvantageous pulse compressions while concurrently transmitting arandomly phase-coded CW waveform.

The operation of CW system 100 is further discussed with reference toFIG. 2. FIG. 2 illustrates an embodiment of one of the plurality ofrange gates RG_(j) as range gate 211. Range gate 211 comprises a phaseconversion module 212 receiving a most recent phase conversion parameter(ϕ_(k)−Θ_(k)) from corrections generator 106 and a demodulated subcodeΘ_(R) from demodulator 109. Phase conversion module 212 converts thephase of the demodulated subcode Θ_(R) using the most recent phaseconversion parameter (ϕ_(k)−Θ_(k)) and generates echo subcode ϕ_(R).Range gate 211 adds the resulting echo subcode ϕ_(R) to a string ofsubcodes {ϕ_(R(i-1)), ϕ_(R(i-2)), ϕ_(R(i-3)) . . . } previously receivedand held in, for example, shift register 213. At each receipt of newecho subcode ϕ_(R), range gate 211 correlates the string of subcodesusing matched filter 214 having a reference register 215, with referenceregister 215 comprising the advantageous set of N polyphase subcodes{ϕ₁, ϕ₂, ϕ₃, . . . ϕ_(N)} utilized by polyphase subcode generator 105.Due to the 2τ(j)+ΔT_(P(j)) delay of the most recent phase conversionparameter (ϕ_(k)−Θ_(k)) among the range gates RG_(j), the phaseconversion operation will provide a string of subcodes {ϕ_(R(i-1)),ϕ_(R(i-2)), ϕ_(R(i-3)) . . . } closely mirroring the N polyphasesubcodes {ϕ₁, ϕ₂, ϕ₃, . . . ϕ_(N)} only if range gate 211 corresponds tothe range interval where a modulated echo Θ′_(R) originated, and providesubstantially noise otherwise. As a result, when range gate 211corresponds to the range interval where the modulated echo Θ′_(R)originated, matched filter 214 provides the advantageous pulsecompression enabled by the N polyphase subcodes {ϕ₁, ϕ₂, ϕ₃, . . .ϕ_(N)}, and generally produces a noisy output otherwise. The compressionof matched filter 214 is subsequently provided to integrator 216 andoutput 217. The phase conversion module 212 may generate an specificecho subcode ϕ_(R(S)) from a specific demodulated subcode Θ_(R(S)) and aspecific most recent phase conversion parameter (ϕ_(k)−Θ_(k))_((S))using an operation such as a digital process, an analog process, or somecombination therein.

It is understood that although the N polyphase subcodes {ϕ₁, ϕ₂, ϕ₃, . .. ϕ_(N)} utilized for correlation as described above may comprise a setof N repeating polyphase subcodes, this is not required. In someembodiments, polyphase subcode generator 105 utilizes a non-repeatingset of polyphase subcodes and corrections generator 106 acts toadditionally provide each subcode ϕ_(i) comprising a phase conversionparameter (ϕ_(i)−Θ_(i)) to each range gate with a delay similar to thatutilized for the phase conversion parameter (ϕ_(i)−Θ_(i)), in order thatthe range gate may update its matched filter template in a mannersimilar to updating the string of subcodes {ϕ_(R(i-1)), ϕ_(R(i-2)),ϕ_(R(i-3)) . . . }. However in certain embodiments, polyphase subcodegenerator 105 utilizes a set of N polyphase subcodes in a repeatingsequential order, and in other embodiments, a matched filter comprisinga range gate comprises a reference register, and the reference registercomprises each of the polyphase subcodes arrayed in the sequentialorder.

It is additionally understood that the delays D such as D₁, D₂, D₃, . .. , D_(m) formulated as, for example, as (τ×j)+ΔT_(P(j)) may be explicitmeasures of time, or alternatively may be determined based on somedatabase or other index b, where b is generated and updated based oneach generation of a random subcode Θ_(i) generally having the subpulsewidth τ, or based on transmission of a modulated subcode Θ′_(i)generally having the subpulse width τ, or both. For example, when timingcircuit 110 provides clocking signals to random waveform generator 101and polyphase subcode generator 105 for the coordinated generation ofthe random subcode Θ_(i), the polyphase subcode ϕ_(i), and supply of therespective subcodes to corrections generator 106, corrections generator106 may generate a phase conversion parameter (ϕ_(i)−Θ_(i))_(b) forstorage in a database indexed by b. Similarly, in a synchronizedoperation, the time t, corresponding to transmission of a givenmodulated subcode Θ′_(i) may be associated with the index b. As aresult, based on the clocking signals and the synchronization of timingcircuit 110, index b itself may be utilized as a counter for theappropriate passage of time. In certain embodiments, CW system 100 mayoperate by providing phase conversion parameters to each range gateRG_(j) based on signals provided by timing circuit 110 and provide aphase conversion parameter (ϕ_(i)−Θ_(i))_((b-j)) to each range gateRG_(j). For example, when the operations of CW system 100 aresynchronized based on signals from timing circuit 110 and an index (b-0)is associated with a transmission time at a time t_(i), the timingcircuit 110 may provide a signal directing corrections generator 106 toprovide a phase conversion parameter (ϕ_(i)−Θ_(i))_((b-1)) to RG₁, aphase conversion parameter (ϕ_(i)−Θ_(i))_((b-2)) to RG₂, and phaseconversion parameter (ϕ_(i)−Θ_(i))_((b-m)) to a range gate RG_(m). CWsystem 100 may use any appropriate indexing scheme in order to track theprovision of phase conversion parameters to specific range gatesfollowing appropriate delays.

An exemplary illustration of the random subcodes Θ_(i) which might begenerated by random waveform generator 101 is shown at FIG. 3, whichdepicts a plurality of subcodes Θ_(i) extending over a time period withthe time period divided into substantially equal subpulse widths τ. AtFIG. 3, the plurality of random subcodes Θ_(i) defines a phase valuebetween 0 and 360 degrees. Random waveform generator 101 provides arandom subcode Θ_(i) between 0 and 360 at each τ, such as the randomsubcode Θ₁ at a first τ, the random subcode Θ₂ at a second τ, and so on.The phase values generated across the time period depicted are generallyindicated by circles. Random waveform generator 101 communicates therandom subcodes Θ_(i) to modulator 103 and further to correctionsgenerator 106, as discussed.

Modulator 103 receives the random subcodes Θ, and upconverts each randomsubcode Θ_(i) to a modulated subcode Θ′_(i). A plurality of modulatedsubcodes Θ′_(i) generated by modulator 103 in response to a plurality ofsubcodes Θ_(i) provided by random waveform generator 101 is illustratedat FIG. 4 as the phase-coded waveform generally indicated by 420. Themodulated subcodes Θ′_(i) comprising phase-coded waveform 420 extendover a time period divided into substantially equal subpulse widths τand are phase shifted relative to each other, with the respective phasesof each modulated subcode Θ′_(i) based on the corresponding randomsubcode Θ_(i). For example at FIG. 4, the modulated subcode Θ′_(i)extends over τ₁ with a phase angle at the commencement of τ₁ of p₁,while the modulated subcode Θ′₁ extends over τ₂ with a phase angle atthe commencement of τ₂ of p₂. Additional phase angles utilized acrossthe time period depicted are generally indicated by circles. Aspreviously discussed, each modulated subcode Θ′_(i) is anelectromagnetic signal having a frequency and a phase over a subpulsewidth τ, where the frequency is typically fixed and the phase isdependent on the most recent random subcode Θ_(i) received. Modulator103 communicates the plurality of modulated subcodes Θ′_(i) comprisingphase-coded waveform 420 to transmitting antenna 104, which transmitsphase-coded waveform 420.

Further as previously discussed, polyphase subcode generator 105produces a polyphase subcode ϕ_(i) corresponding to each random subcodeΘ_(i). A plurality of polyphase subcodes ϕ_(i) generated by polyphasesubcode generator 105 and corresponding to individual random subcodesΘ_(i) comprising a plurality of random subcodes Θ_(i) is illustrated atFIG. 5. At FIG. 5, the plurality of polyphase subcodes ϕ_(i) extendsover a time period with the time period divided into substantially equalsubpulse widths τ, and define a phase value between 0 and 360 degrees.Polyphase subcode generator 105 provides a polyphase subcode ϕ_(i)between 0 and 360 at each τ, such as the polyphase subcode ϕ₁ at a firstτ, the polyphase subcode ϕ₂ at a second τ, and so on. Each polyphasesubcode ϕ_(i) is a member of a set of polyphase subcodes having at leastN number of members, where N may be any quantity and typically definessome phase-coding scheme. Polyphase subcode generator 105 communicatesthe polyphase subcodes ϕ_(i) to corrections generator 106, as discussed.

Corrections generator 106 receives each random subcode Θ_(i) such asthose illustrated at FIG. 3 and a corresponding polyphase subcode ϕ_(i)such as those illustrated at FIG. 5, and generates a phase conversionparameter (ϕ_(i)−Θ_(i)) using the subcode Θ_(i) and the correspondingpolyphase subcode ϕ_(i).

Additionally provided and illustrated at FIG. 6 is an apparatus for acontinuous wave radar system 600 comprising one or more digitalprocessors 640, and a monostatic antenna system generally indicated at641, with monostatic antenna system 641 comprising antenna 604 andcirculator 650. The processors 640 are programmed to perform stepscomprising generating a random subcode Θ_(i) at 601 and generating apolyphase subcode ϕ_(i) corresponding to the random subcode Θ_(i) at605. In particular embodiments, the operations at 601 and 605 aregenerally synchronized via communication from a clock CLK, asillustrated. As before the polyphase subcode ϕ_(i) is a member of a setof polyphase subcodes having N number of members. Processors 640communicate the subcode Θ_(i) and polyphase subcode ϕ_(i) to acorrections generator 606 for generation of a phase conversion parameter(ϕ_(i)−Θ_(i)) corresponding to the subcode Θ_(i). Processors 640 furthercommunicate the subcode Θ_(i) and modulate the subcode Θ_(i) producingmodulated subcode Θ′_(i) at 603, and further communicate the modulatedsubcode Θ′_(i) to antenna system 641, typically via additionalamplifying and conditioning components (not shown). Typically CLK isadditionally in communication with operation 603 or antenna system 641in order to enable transmission of the modulated subcode Θ′_(i) at aparticular transmission time t_(i).

Processors 640 further provide the phase conversion parameter(ϕ_(i)−Θ_(i)) to each range gate RG_(j) comprising a plurality of rangegates, as previously discussed. Communication of the phase conversionparameter (ϕ_(i)−Θ_(i)) occurs following a delay after the transmissiontime t_(i), with the delay unique to the each range gate RG_(j) asbefore. This is illustrated at FIG. 6, where processors 640 provide thephase conversion parameter (ϕ_(i)−Θ_(i)) to a sequence of operations 642following the delay D_(j). The sequence of operations 642 isrepresentative of operations previously discussed which occur within agiven range gate RG_(j). Having generated the random subcode Θ_(i),modulated subcode Θ′_(i), and polyphase subcode ϕ_(i) corresponding to agiven subpulse width τ, and having generated and provided the phaseconversion parameter (ϕ_(i)−Θ_(i)) to the sequence of operations 642, at641, processors 640 repeat the processes and conduct 601, 603, 605, 606,and the appropriate delay D_(j) generally for every subsequent subpulsewidth τ. This repetition typically occurs independently of any echoprocessing steps that occur within processors 640. Within the sequenceof operations 642 and following the delay D_(j), the phase conversionparameter (ϕ_(i)−Θ_(i)) is provided to operation 635, which identifiesthe most recent phase conversion parameter (ϕ_(k)−Θ_(k)). Typically themost recent phase conversion parameter (ϕ_(k)−Θ_(k)) is the latest phaseconversion parameter (ϕ_(i)−Θ_(i)) received. Operation 635 communicatesthe most recent phase conversion parameter (ϕ_(k)−Θ_(k)) to phaseconversion operation 612.

As processors 640 conduct operations 601, 603, 605, 606, and D_(j),processors 640 additionally receive modulated echo returns Θ′_(R) fromantenna system 641, typically via additional amplifying and conditioningcomponents (not shown). Processors 640 demodulates the modulated echoreturn Θ′_(R) at operation 634, generating demodulated subcode Θ_(R), asbefore. Processors 640 provide the demodulated subcode Θ_(R) to phaseconversion operation 612 which converts the demodulated subcode Θ_(R)using the most recent phase conversion parameter (ϕ_(k)−Θ_(k)) receivedfrom 635, producing an echo subcode ϕ_(R), as before. In someembodiments, CLK is in communication with operation 634 and delay D_(j),in order to indicate when the demodulated subcode Θ_(R) is provided byoperation 634 and provide an appropriate processing time ΔT_(P(j)) to beutilized in delay D_(j).

Operation 637 adds the resulting echo subcode ϕ_(R) to a polyphasesequence comprising a string of subcodes, illustrated as {ϕ_(R(i)),ϕ_(R(i-1)), ϕ_(R(i-2)) . . . ϕ_(R(N))} at FIG. 6. At operation 638,processors 640 correlate the updated polyphase sequence using the set ofpolyphase subcodes ϕ_((i)), ϕ_((i-1)), ϕ_((i-2)) . . . ϕ_((N)) utilizedin operation 605 using, in certain embodiments, shift register 613 andreference register 615. The correlation provides an output O_(i) whichis communicated to integration operation 639. Integration operation 639subsequently communicates the integrated output to output operation 640.

The method, system, and apparatus provided thereby discloses a manner bywhich a random CW waveform may be transmitted while enabling therecovery of polyphase subcodes {ϕ1, ϕ₂, ϕ₃, . . . ϕ_(N)} advantageousfor the purposes of correlation and pulse compression. The apparatus andmethodology differs substantially from that employed by typical randomradars transmitting randomly phase coded CW waveforms, which generallyrecords and updates a series of echo subcodes received for comparisonagainst a delayed replica for determination of RTT. Further, because therandom transmitted waveform is typically correlated against the (alsorandom) delayed replica, any ability to generate advantageous phasecodes is lost. In contrast, the system, method, and apparatus disclosedhere provides for transmission of a random CW waveform while alsoallowing the use of any phase code {ϕ₁, ϕ₂, . . . ϕ_(N)} that lendsitself to advantageous pulse compressions.

In a typical embodiment, each individual range gate RG_(j) has anassociated D_(RG(j)) where the associated D_(RG(j)) is equal to(τ×j)+ΔT_(P(j)), and the phase conversion parameter (ϕ_(i)−Θ_(i)) isprovided to the each individual range gate RG_(j) such that0.8≤D_(j)/D_(RG(j))≤1.2, where D_(j) is the delay D_(j) unique to theeach individual range gate RG_(j) and D_(RG(j)) is the associatedD_(RG(j)). In certain embodiments, 0.9≤D_(j)/D_(RG(j))≤1.1, and in otherembodiments, 0.95≤D_(j)/D_(RG(j))≤1.05. The associated processing timeperiod ΔT_(P(j)) may differ among the various range gates RG_(j), or maybe a time period common to all range gates.

In other embodiments, the digital process, analog process, orcombination used to generate the specific phase conversion parameter(ϕ_(i(S))−Θ_(i(S))) performs operations equivalent to(ϕ_(i(S))−Θ_(i(S)))=ƒ₁ (ϕ_(i(S)), Θ_(i(S))) where ƒ₁ is a mathematicalfunction over at least some portion of a domain comprising ϕ_(i(S)) andΘ_(i(S)), and where (ϕ_(i(S))−Θ_(i(S))) is the specific phase conversionparameter (ϕ_(i(S))−Θ_(i(S))), ϕ_(i(S)) is the specific polyphasesubcode ϕ_(i(S)), and Θ_(i(S)) is the specific random subcode Θ_(i(S)).

In another embodiment, phase conversion module 212 performs operationsequivalent to ϕ_(R(S))=ƒ₂ ((ϕ_(k)−Θ_(k))_((S)), Θ_(R(S))) where ƒ₂ is amathematical function over at least some portion of a domain comprising(ϕ_(k)−Θ_(k))_((S)) and Θ_(R(S)), and where when0.8≤Θ_(i(S))/Θ_(R(S))≤1.2 and0.8≤(ϕ_(i(S))−Θ_(i(S))/(ϕ_(k)−Θ_(k))_((S))≤1.2, then0.8≤ϕ_(i(S))/ϕ_(R(S))≤1.2, where Θ_(i(S)) is one of the random subcodesΘ_(i) generated by the random wave form generator, ϕ_(i(S)) is thespecific polyphase subcode ϕ_(i(S)) generated by the correctionsgenerator for the Θ_(i(S)), Θ_(R(S)) is the specific demodulated subcodeΘ_(R(S)), (ϕ_(i(S))−Θ_(i(S))) is the specific phase conversion parameter(ϕ_(i(S))−Θ_(i(S))) generated by the corrections generator for theΘ_(i(S)) and ϕ_(i(S)), and (ϕ_(k)−Θ_(k))_((S)) is the specific mostrecent phase conversion parameter (ϕ_(k)−Θ_(k))_((S)). In otherembodiments, the function ƒ₂ is substantially an inverse function of thefunction ƒ₁ used by corrections generator 106, such that when(ϕ_(i(S))−Θ_(i(S)))=f₁ (ϕ_(i(S)), Θ_(i(S))) and aϕ₀=ƒ₂((ϕ_(i(s))−Θ_(i(S)))_((S)), Θ_(i(S))), then 0.8≤ϕ_(i(S))/(ϕ₀≤1.2.In certain embodiments when 0.9≤Θ_(i(S))/Θ_(R(S))≤1.1 and0.9≤(ϕ_(i(S))−Θ_(i(S))/(ϕ_(k)−Θ_(k))_((S))≤1.1 then0.9≤ϕ_(i(S))/ϕ_(R(S))≤1.1, and in other embodiments when0.95≤Θ_(i(S))/Θ_(R(S))≤1.05 and0.95≤(ϕ_(i(S))−Θ_(i(S))/(ϕ_(k)−Θ_(k))_((S))≤1.05 then 0.95ϕ_(i(S))/ϕ_(R(S))≤1.05. In some embodiments when ϕ_(i(S))−Θ_(i(S)))=ƒ₁(ϕ_(i(S)), Θ_(i(S))) and the ϕ₀=ƒ₂((ϕ_(i(s))−Θ_(i(S)))_((S)), Θ_(i(S))),then 0.9≤ϕ_(i(S))/(ϕ₀≤1.1, and in further embodiments then0.95≤ϕ_(i(S))/ϕ₀≤1.05.

Additionally, in some embodiments, a “random subcode Θ_(i)” means one ofa plurality of random subcodes Θ_(i), where the plurality of randomsubcodes Θ_(i) defines a plurality of phases over some time period andthe plurality of phases over the time period generally comprises aprobability density function (μ,σ²) having a mean μ and a variance σ²,such as a Normal, Beta, Uniform, Weibull, or other distributions knownin the art. In some embodiments, each phase p comprising the pluralityof phases satisfies a relationship 0.8≤p/x_(PDF)≤1.2, where x_(PDF) is apoint on the probability density function (μ,σ²). In other embodiments0.9≤p/x_(PDF)≤1.1, and in other embodiments 0.95≤p/x_(PDF)≤1.05. Thegeneration of such random phases may be conducted using means known inthe art, such as noise-generating microwave sources, digital generationusing a processor, or others. See e.g., Axellson, “Noise Radar UsingRandom Phase and Frequency Modulation,” IEEE Transactions on Geoscienceand Remote Sensing 42(11) (2004), and see K. Kulpa, Signal Processing inNoise Waveform Radar (2013), and see G. R. Cooper and C. D. McGillem,Random Signal Radar, Final Rep. TR-EE67-11 (1967), among many others.

Further and in other embodiments, “modulated subcode Θ′_(i)” means anelectromagnetic signal having a frequency and a phase over a subpulsewidth τ, where the phase defines a value of the modulated subcode Θ′_(i)at some point during the subpulse width τ, and where the phase is basedon a random subcode Θ_(i). In certain embodiments, the phase defines thevalue of the modulated subcode Θ′_(i) at the commencement of thesubpulse width τ. In certain embodiments, the phase is a mathematicalfunction of the random subcode Θ_(i). In other embodiments, a parameterP₀ is a function of a specific random subcode Θ₀) such thatP₀=ƒ₃(Θ_(i(P))) where Θ_(i(P)) denotes the specific random subcodeΘ_(i(P)) and where ƒ₃ is a mathematical function over at least someportion of a domain comprising Θ_(i(P)), and the phase for the specificrandom subcode Θ_(i(P)) has a value such that 0.8≤p/P₀≤1.2 in oneembodiment, 0.9≤p/P₀≤1.1 in a another embodiment, and 0.95≤p/P₀≤1.05 ina further embodiment, where p is the phase of the modulated subcodeΘ′_(i). In other embodiments, the frequency of the modulated subcodeΘ′_(i) is constant over the subpulse width τ.

Additionally, it is understood that although the foregoing discussionsdiscuss generation of an individual random subcode Θ_(i), in preparationfor transmitting a specific modulated subcode Θ′_(i) at a transmissiontime t_(i), and generation of an individual polyphase subcode ϕ_(i)corresponding to the specific modulated subcode Θ′_(i), and generationof an individual phase correction parameter (ϕ_(i)−Θ_(i)) correspondingto the specific modulated subcode Θ′_(i), it is not required thatgeneration of the individual random subcode Θ_(i), the individualpolyphase subcode ϕ_(i), or the individual phase correction parameter(ϕ_(i)−Θ_(i)) be temporally related to the transmission time t_(i) ofthe specific modulated subcode Θ′_(i), except to the extent necessaryfor a modulator such as 103 to upconvert a random subcode Θ_(i) to amodulated subcode Θ′_(i) and for a corrections generator such as 106 toprovide a properly delayed phase correction parameter (ϕ_(i)−Θ_(i))comprising the random subcode Θ_(i) corresponding to the modulatedsubcode Θ′_(i).

Further, it is understood that CW system 100 is typically intended tooperate as a continuous wave radar system exhibiting a high duty cycle,where here “duty cycle” means the proportion of a given time period whentransmitting antenna 104 emits modulated subcodes Θ′_(i). In certainembodiments. CW System 100 exhibits a duty cycle of at least ½, in otherembodiments at least 7/10, and in further embodiments at least 9/10.

Further it is understood that, although FIG. 1 depicts a bistatic systemcomprising both transmitting antenna 104 and a separate receivingantenna 108, this is not intended as a limitation on the disclosure.Alternatively, CW system 100 could be a monostatic system wheretransmitting antenna 104 and receiving antenna 108 are a single antenna,and communications from modulator 103 and to demodulator 109 aredirected using a circulator, as is known in the art of CW radar systems.

Further it is understood that the functions of various componentsdescribed herein may be performed using analog or digital means. Incertain embodiments, CW system 100 comprises one or more digitalprocessors, and the one or more digital processors are programmed withinstructions for performing some or all of the functions of randomwaveform generator 101, modulator 103, polyphase subcode generator 105,corrections generator 106, the plurality of range gates RG_(j), orvarious combinations thereof.

FIGS. 7 and 8 illustrate a specific embodiment of the manner in whichthe random waveform generator 101, polyphase subcode generator 105, andcorrections generator 106 of CW system 100 act to provide a properlydelayed most recent phase conversion parameter (ϕ_(k)−Θ_(k)) to eachrange gate in order to allow recovery of underlying polyphase subcodes{ϕ₁, ϕ₂, ϕ₃, . . . ϕ_(N)}. FIG. 7 illustrates a series of parametersgenerally indicated by random subcode Θ_(i), polyphase subcode ϕ_(i),phase conversion parameter (ϕ_(i)−Θ_(i)), and modulated subcode Θ′igenerated by CW system 100 in support of transmitting the modulatedsubcodes via transmitting antenna 104 over time periods generallyindicated by Transmission time t_(i). In support of transmission at theTransmission time t_(i) of 0<t₁≤1τ, random waveform generator 101generates the random subcode Θ₁, and polyphase subcode generator 105produces the polyphase subcode ϕ₁ corresponding to the random subcodeΘ₁. Random waveform generator 101 communicates the random subcode Θ₁ andpolyphase subcode generator 105 communicates the polyphase subcode ϕ₁ tocorrections generator 106, which generates the phase conversionparameter (ϕ₁−Θ₁) corresponding to the random subcode Θ₁. Additionally,random waveform generator 101 communicates random subcode Θ₁ tomodulator 103 which upconverts random subcode Θ₁ to modulated subcodeΘ′₁, and transmitting antenna 104 transmits the modulated subcode Θ′₁over the transmission time 0<t₁≤1τ. Similarly in support of transmissionat the Transmission time t_(i) of 1τ<t₁≤2τ, random waveform generator101 generates random subcode Θ₂, polyphase subcode generator 105produces polyphase subcode ϕ₂, corrections generator 106 generates phaseconversion parameter (ϕ₂−Θ₂), and further random waveform generator 101communicates random subcode Θ₂ to modulator 103 for upconversion andtransmission of modulated subcode Θ′₂ via transmitting antenna 104 overTransmission time 1τ <t₂≤2τ. Similar operations occur for transmissionof modulated subcode Θ′₃ over 2τ<t₃≤3τ, modulated subcode Θ′₄ over3τ<t₄≤4τ, modulated subcode Θ′₅ over 4τ<t₅≤5τ, modulated subcode Θ′₆over 5τ<t₆≤6τ, modulated subcode Θ′₇ over 6τ<t₇≤7τ, modulated subcodeΘ′₈ over 7τ<t₈≤8τ, and modulated subcode Θ′₉ over 8τ<t₉≤9τ. Aspreviously discussed, all random subcode Θ_(i) are random phases, andall modulated subcodes Θ′_(i) transmitted are randomly phase codedwaveforms. Note also that in this illustration, polyphase subcodegenerator 105 utilizes a set of repeating polyphase subcodes {ϕ₁, ϕ₂,ϕ₃}, such that corrections generator 106 generates sequential phaseconversion parameters of (ϕ₁−Θ₁), (ϕ₂−Θ₂), (ϕ₃−Θ₃), (ϕ₁−Θ₄), (ϕ₂−Θ₅),(ϕ₃−Θ₆), (ϕ₁−Θ₇), (ϕ₂−Θ₈), and (ϕ₃−Θ₉).

FIG. 8 illustrates the transmission of the modulated subcodes Θ′_(i)from transmitting antenna 104 over the transmission periods generallyindicated by t_(i). For illustration, the transmission commences withtransmitting antenna 104 transmitting the modulated subcode Θ′_(i) over0<t₁≤1τ, and the presence of Θ′₁ as a waveform physically present withina range interval is similarly illustrated at FIG. 8 using rangeintervals generally indicated by RH₀, RH₁, RH₂, and RH₃, whereas beforethe range intervals correspond to a distance substantially equivalent toτc/2. Accordingly, transmitting antenna 104 transmits modulated subcodeΘ′₂ over 1τ<t₂≤2τ, modulated subcode Θ′₃ over 2τ<t₃≤3τ, and so on to thelast illustrated transmission where transmitting antenna 104 transmitsmodulated subcode Θ′₉ over 8τ<t₂≤9τ.

FIG. 8 additionally illustrates a plurality of range gates RG₁, RG₂, andRG₃. The transmission times t_(i) of FIG. 8 apply to all parametershorizontally level with a given t_(i), and the phase conversionparameters sent to the plurality of range gates RG₁, RG₂, and RG₃ fromcorrections generator 106 following appropriate delay are additionallyindicated at each time and for each of RG₁, RG₂, and RG₃. The particularphase conversion parameters indicated for each range gate and at eachtime are the most recent phase conversion parameters (ϕ_(k)−Θ_(k))discussed earlier and received by phase conversion module 212, based onthe appropriate range delay for a given range gate. For example, for thet_(i) commencing at zero and treating a ΔT_(P(1)) as equal to zero forthe purpose of illustration, RG₁ receives the phase correction (ϕ₁−Θ₁)during the period 1τ<t₃≤2τ, based on the delay τ(1)+0=1τ. Similarly, forthe t_(i) commencing at 1τ, RG₁ receives phase correction (ϕ₂−Θ₂) duringthe period 2τ<t₃≤3τ based on the appropriate delay 1τ, and, for thet_(i) commencing at 2τ, receives (ϕ₃−Θ₃) during the period 3τ<t₄≤4τbased on the appropriate delay 1τ. RG₁ continues to receive most recentphase corrections having the appropriate 1τ delay for each correspondingmodulated subcode Θ′_(i) transmitted, through to reception of (ϕ₂−Θ₈)during period 8τ<t₉≤9τ.

In similar fashion, for the t_(i) commencing at zero and with aΔT_(P(2)) equal to zero, RG₂ receives the phase correction (ϕ₁−Θ₁)during the period 2τ<t₃≤3τ, based on the delay τ(2)+0=2τ. For the t_(i)commencing at 1τ, RG₂ receives phase correction (ϕ₂−Θ₂) during theperiod 3τ<t₄≤4τ based on the appropriate delay 2τ, and for the t_(i)commencing at 2τ, receives (ϕ₃−Θ₃) during the period 4τ<t₅≤5τ based onthe appropriate delay 2τ, and so on through to reception of (ϕ₁−Θ₇)during period 8τ<t₉≤9τ. In like manner, for the t_(i) commencing at zeroand with ΔT_(P(3)) equal to zero, RG₃ receives the phase correction(ϕ₁−Θ₁) during the period 3τ<t₄≤4τ, based on the delay τ(3)+0=3τ, andfor the t_(i) commencing at 1τ receives phase correction (ϕ₂−Θ₂) duringthe period 4τ<t₅≤5τ based on the appropriate delay 3τ, and for the t_(i)commencing at 2τ, receives (ϕ₃−Θ₃) during the period 5τ<t₆≤6τ based onthe appropriate delay 3τ. As previously discussed, each respective rangegate RG₁, RG₂, and RG₃ utilizes its most recent phase conversionparameter (ϕ_(k)−Θ_(k)) received from corrections generator 106 to phaserotate any demodulated subcode Θ_(R) received from demodulator 109, inorder to generate an echo subcode ϕ_(R) from the demodulated subcodeΘ_(R).

The impact of the phase conversions based on the properly delayed phasecorrection parameters (ϕ_(i)−Θ_(i)) is illustrated at FIG. 9, whichsimilar to FIG. 8 illustrates the transmission of modulated subcodesΘ′_(i) from transmitting antenna 104, range intervals RH₀, RH₁, RH₂, andRH₃, range gates RG₁, RG₂, and RG₃, and also the properly delayed mostrecent phase conversion parameters (ϕ_(k)−Θ_(k)) for each range gatecorresponding to the listed transmission times. FIG. 9 additionallyillustrates demodulated subcodes Θ_(R) provided by demodulator 109 andarising from an object O₁ located in range interval RH₁. Based on therange intervals of τc/2 and the inherent round trip time (RTT) from theobject O₁ in RH₁, and for a transmission of a modulated subcode Θ′_(i)commencing at t_(i) of zero, and again for illustration using aprocessing time ΔT_(P) equal to zero, each range gate RG₁, RG₂, and RG₃is expected to initially receive the demodulated subcode Θ₁ of the echofrom demodulator 109 during the time interval over 1τ<t₂≤2τ, asillustrated for each range gate. In similar fashion and based on theexpected RTT corresponding to the object O₁, RG₁, RG₂, and RG₃ eachreceive the demodulated subcode Θ₂ of the echo during 2τ<t₃≤3τ.Additionally at 2τ<t₃≤3τ and due to the range interval of τc/2, RG₁,RG₂, and RG₃ also receives the back half of the demodulated subcode Θ₁,as indicated. Similarly and for similar reasons, RG₁, RG₂, and RG₃receive demodulated subcode Θ₃ and Θ₂ of the echo during 3τ<t₅≤4τ, thedemodulated subcode Θ₄ and Θ₃ of the echo during 4τ<t₅≤5τ, and so on tothe reception of the demodulated subcode Θ₈ and Θ₇ of the echo during8τ<t₉≤9τ. Similar to FIG. 8, for each range gate, the most recent phaseconversion parameters (ϕ_(k)−Θ_(k)) provided to the phase conversionmodule 212 of each respective range gate is additionally indicated. Forillustrative purposes at FIG. 9, leakage signals contributions areignored but will be discussed subsequently.

As can be recognized at FIG. 9, beginning at 1τ<t₂≤2τ, for an object O₁located within RH₁, the most recent most recent phase conversionparameter (ϕ_(k)−Θ_(k)) provided to RG₁ in conjunction with thedemodulated subcode Θ_(R) present at the range gates allows the phaseconversion module of RG₁ to phase rotate the demodulated subcode Θ_(R)and produce an echo subcode ϕ_(R-1) generally equivalent to one of therepeating ϕ₁, ϕ₂, or ϕ₃ polyphase subcodes utilized by polyphase subcodegenerator 105 in this example. For example, phase conversions by a phaseconversion module such as 212 would substantially produce echo subcodesϕ_(R-1) of ϕ₁ at 1τ<t₃≤2τ, ϕ₂ at 2τ<t₃≤3τ, ϕ₃ at 3τ<t₄≤4τ, again ϕ₁ at4τ<t₅≤5τ, ϕ₂ at 5τ<t₆≤6τ, ϕ₃ at 6τ<t₇≤7τ, and again ϕ₁ at 7τ<t₈≤8τ, andϕ₂ at 8τ<t₉≤9τ. Relative to a shift register such as 213 and a referenceregister 215 comprising the ϕ₁, ϕ₂, and ϕ₃ polyphase subcodes, matchedfilter 214 would generate optimized pulse compressions generally eachtime the phase conversion module 212 adds the resulting echo subcodeϕ_(R-1) to the string of subcodes and {ϕ₁, ϕ₂, ϕ₃} are ordered withinshift register 213. Meanwhile at FIG. 9, because of the delayed phaseconversion parameters (ϕ_(k)−Θ_(k)) present at RG₂ and RG₃, phaseconversions do not produce one of ϕ₁, ϕ₂, or ϕ₃ but rather generateanother random subcode φ_(random), and the respective matched filters ofthose range gates substantially generate noise signals. Thus for theobject O₁ within the range interval RH₁, the properly delayed phaseconversion parameters (ϕ_(i)−Θ_(i)) provided to each range gategenerates pulse compression in the appropriate range bin while generallyresulting in noise generation in other range bins.

FIG. 10 illustrates the impact of the properly delayed phase conversionparameters (ϕ_(i)−Θ_(i)) based on demodulated subcodes Θ_(R) provided bydemodulator 109 and arising from an object O₂ located in range intervalRH₂. As illustrated, beginning at 2τ<t₃≤3τ, for the object O₂ withinRH₂, the most recent most recent phase conversion parameter(ϕ_(k)−Θ_(k)) provided to RG₂ allows the phase conversion module of RG₂to phase rotate the demodulated subcode Θ_(R) and produce echo subcodesϕ_(R-2) generally equivalent to one of ϕ₁, ϕ₂, or ϕ₃. The properlydelayed phase conversion parameters (ϕ_(i)−Θ_(i)) provided to theremaining range gates produce additional random subcodes φ_(random).

FIG. 11 illustrates the impact of the properly delayed phase conversionparameters (ϕ_(i)−Θ_(i)) when CW system receives demodulated subcodesΘ_(R) provided by demodulator 109 and arising concurrently from anobject O₁ in range interval RH₁, an object O₂ in range interval RH₂, andan object O₃ in range interval RH₃. As before, based on range intervalsof τc/2 and the expected RTT for O₁ in RH₁, each range gate wouldinitially receive the demodulated subcode Θ₁ during the time intervalover 1τ<t₂≤2τ, and chronologically receive Θ₂ through Θ₈ over theremaining time intervals illustrated, as well as the back half duringsubsequent time periods as before. Similarly and in addition, and basedon the expected RTT for O₂ in RH₂, each range gate would further beginreceiving the demodulated subcode Θ₁ during the time interval over2τ<t₃≤3τ, and due to continuing echoes from O₂ chronologically receiveΘ₁ through Θ₇ over the remaining time intervals illustrated. Further,and based on the expected RTT for O₃ in RH₃, each range gate wouldadditionally begin receiving the demodulated subcode Θ₁ during the timeinterval over 3τ<t₄≤4τ, and due to continuing echoes from O₃chronologically receive Θ₂ through Θ₆ over the remaining time intervalsillustrated. As a result, each range gates receives multiple demodulatedechoes. However, due to the properly delayed phase conversion parameters(ϕ_(i)−Θ_(i)) also illustrated at FIG. 11 for each range gate, thesubsequent phase conversions of RG₁ will largely produce echo subcodesϕ_(R-1) approximating ϕ₁ at 1τ<t₂≤2τ, ϕ₂ at 2τ<t₃≤3τϕ₃ at 3τ<t₄≤4τ, ϕ₁at 4τ<t₅≤5τ, ϕ₂ at 5τ<t₆≤6τ, ϕ₃ at 6τ<t₇≤7τ, ϕ₁ at 7τ<t₈≤8τ, and ϕ₂ at8τ<t₉≤9τ, while the phase conversions of RG₂ will largely produce echosubcodes ϕ_(R-2) approximating ϕ₁ at 2τ<t₃≤3τ, ϕ₂ at 3τ<t₄≤4τ, ϕ₃ at4τ<t₅≤5τ, ϕ₁ at 5τ<t₆≤6τ, ϕ₂ at 6τ<t₇≤7τ, ϕ₃ at 7τ<t₈≤8τ, and ϕ₁ at8τ<t₉≤9τ, while the phase conversions of RG₃ will largely produce echosubcodes ϕ_(R-3) approximating ϕ₁ at 3τ<t₄≤4τ, ϕ₂ at 4τ<t₅≤5τ, ϕ₃ at5τ<t₆≤6τ, ϕ₁ at 6τ<t₇≤7τ, ϕ₂ at 7τ<t₈≤8τ, and ϕ₃ at 8τ<t₉≤9τ. Thus, asdisclosed, CW system 100 provides the significant capability of enablingthe recovery of an underlying phase code {ϕ₁, ϕ₂, . . . ϕ_(N)} followingreturn of a modulated echo Θ′_(R), using a randomly phase coded CWwaveform.

In addition to the advantage of enabling recovery of the underlyingphase code {ϕ₁, ϕ₂, . . . ϕ_(N)}, the use of the delayed phase codecorrections in the manners described additionally has the significantadvantage of allowing for CW transmission while minimizing the impact ofsignal leakage. As is understood and as discussed above, in any CWsystem, during an analogous transmission of a modulated subcode Θ′_(i)at a time t_(i), some degree of leakage of the modulated subcode Θ′_(i)is experienced by the receiving components of the system, degrading theability of the receiving components to separate and discriminate amodulated echo Θ′_(R). However, the particular manner of providing phaseconversion parameters to the respective range gates provided by thisdisclosure act to significantly mitigate the impact of this leakage inany subsequent processing. This is illustrated at FIG. 12 which, similarto FIG. 10, illustrates demodulated subcodes Θ_(R) provided to RG₁, RG₂,and RG₃ arising from an object O₂ located in range interval RH₂. Inaddition, in parenthesis and italicized, leakage signals received byeach range gate are also indicated based on the current modulatedsubcode Θ′_(i) being transmitted via transmitting antenna 104. FIG. 12also illustrates the properly delayed phase conversion parameters(ϕ_(i)−Θ_(i)) provided to each range gate RG_(j), including those phaseconversion parameters that correspond to prior modulated subcodes Θ′_(i)(not shown) that preceded the transmission of Θ′₁ during 0<t₁≤1τ. Theprior phase conversion parameters which precede (ϕ₁−Θ₁) are indicated as(ϕ₀−Θ₀), (Θ⁽⁻¹⁾−Θ⁽⁻¹⁾), and (ϕ⁽⁻²⁾−Θ⁽⁻²⁾). At FIG. 12, and as a resultof the properly delayed phase conversion parameters provided to eachrange gate, conversion of the leakage signals using the most recentphase conversion parameter (ϕ_(k)−Θ_(k)) at each respective range gateacts to generate another random subcode φ_(random), rather than one ofϕ₁, ϕ₂, or ϕ₃. However, beginning at 2τ<t₃≤3τ as before, for the objectO₂ within RH₂, the most recent most recent phase conversion parameter(ϕ_(k)−Θ_(k)) provided to RG₂ allows the phase conversion module of RG₂to phase rotate the demodulated subcode Θ_(R) and produce echo subcodes(1 m-2 generally equivalent to one of ϕ₁, ϕ₂, or ϕ₃. The properlydelayed phase conversion parameters (ϕ_(i)−Θ_(i)) thereby significantlymitigate the impact of any leakage signals on CW system 100 that arisefrom the modulated subcode Θ′_(i) currently being transmitted.

Thus, provided here is method, system, and apparatus by which a randomCW radar waveform may be transmitted while enabling the recovery ofpolyphase subcodes {ϕ₁, ϕ₂, ϕ₃, . . . ϕ_(N)} advantageous for thepurposes of correlation and pulse compression. The CW system transmitsand receives a random waveform while avoiding the necessary use of adelayed replica for RTT determination, by providing properly delayedphase conversion parameters (ϕ_(i)−Θ_(i)) from a corrections generatorto various range gates RG_(j) comprising a plurality of range gates. Theassociated methodology of the CW radar system has the significantadvantage of enabling recovery of the underlying phase code {ϕ₁, ϕ₂, . .. ϕ_(N)} associated with a given {Θ₁, Θ₂, . . . Θ_(N)} series ofmodulated subcodes Θ′_(i) transmitted, based on the phase conversionparameters (ϕ_(i)−Θ_(i)) appropriately delayed and provided by thecorrections generator. This allows use of any phase code {ϕ₁, ϕ₂, . . .ϕ_(N)} that lends itself to advantageous pulse compressions whileconcurrently enabling transmission of a randomly phase-coded waveform.

Accordingly, this description provides exemplary embodiments of thepresent invention. The scope of the present invention is not limited bythese exemplary embodiments. Numerous variations, whether explicitlyprovided for by the specification or implied by the specification ornot, may be implemented by one of skill in the art in view of thisdisclosure.

It is to be understood that the above-described arrangements are onlyillustrative of the application of the principles of the presentinvention and it is not intended to be exhaustive or limit the inventionto the precise form disclosed. Numerous modifications and alternativearrangements may be devised by those skilled in the art in light of theabove teachings without departing from the spirit and scope of thepresent invention. It is intended that the scope of the invention bedefined by the claims appended hereto.

In addition, the previously described versions of the present inventionhave many advantages, including but not limited to those describedabove. However, the invention does not require that all advantages andaspects be incorporated into every embodiment of the present invention.

All publications and patent documents cited in this application areincorporated by reference in their entirety for all purposes to the sameextent as if each individual publication or patent document were soindividually denoted.

What is claimed is:
 1. A method of transmitting a continuous wavephase-modulated random radar signal and processing echo returnscomprising: generating the continuous wave phase-modulated random radarsignal by: generating a random subcode Θ_(i); producing a polyphasesubcode ϕ_(i) corresponding to the random subcode Θ_(i) where thepolyphase subcode ϕ_(i) is a member of a set of polyphase subcodeshaving N number of members; transmitting a modulated subcode Θ′_(i) froman antenna system during a subpulse width τ where τ is a measure oftime, and where the modulated subcode Θ′_(i) is an electromagneticsignal having a phase over the subpulse width τ, where the phase isbased on the random subcode Θ_(i); generating a phase conversionparameter (ϕ_(i)−Θ_(i)) using the random subcode Θ_(i) and the polyphasesubcode ϕ_(i) and providing the phase conversion parameter (ϕ_(i)−Θ_(i))to a plurality of range gates comprising two or more range gates RG_(j),where j is an integer unique to each range gate RG_(j) and j is greaterthan or equal to 1, by providing the phase conversion parameter(ϕ_(i)−Θ_(i)) to the each individual range gate RG_(j) following a delayD_(j) after transmission of the modulated subcode Θ′_(i) from theantenna system, where the delay D_(j) is unique to the each individualrange gate RG_(j); and repeating the generating the random subcode Θ_(i)step, the producing the polyphase subcode ϕ_(i) step, the transmittingthe modulated subcode Θ′_(i) step, and the generating the phaseconversion parameter (ϕ_(i)−Θ_(i)) using the random subcode Θ_(i) andthe polyphase subcode ϕ_(i) and providing the phase conversion parameter(ϕ_(i)−Θ_(i)) step, thereby transmitting the continuous wavephase-modulated random radar signal; and receiving an echo return of thecontinuous wave phase-modulated random radar signal and processing theecho return using the plurality of range gates RG_(j), therebyprocessing echo returns.
 2. The method of claim 1 where receiving theecho return of the continuous wave phase-modulated random radar signaland processing the echo return using the plurality of range gates RG_(j)further comprises: receiving the echo return from the antenna system;demodulating the echo return and producing a demodulated subcode Θ_(R);and providing the demodulated subcode Θ_(R) to the plurality of rangegates RG_(j).
 3. The method of claim 2 further comprising processing thedemodulated subcode Θ_(R) by, at the each range gate RG_(j) byperforming steps comprising: receiving the demodulated subcode Θ_(R);identifying a most recent phase conversion parameter (ϕ_(k)−Θ_(k))received from the corrections generator, where the most recent phaseconversion parameter (ϕ_(k)−Θ_(k)) is the phase conversion parameter(ϕ_(i)−Θ_(i)) most recently provided to the each range gate RG_(j);generating an echo subcode ϕ_(R) by converting the demodulated subcodeΘ_(R) using the most recent phase conversion parameter (ϕ_(k)−Θ_(k));modifying a polyphase sequence comprising a string of subcodes by addingthe echo subcode ϕ_(R) to the polyphase sequence, thereby generating anupdated polyphase sequence; and correlating the updated polyphasesequence using the set of polyphase subcodes having N number of membersused by the polyphase subcode generator, thereby processing thedemodulated subcode Θ_(R).
 4. The method of claim 3 where the each rangegate RG_(j) has an associated D_(RG(j)) where the associated D_(RG(j)),is equal to 2τ(j)+ΔT_(P), where ΔT_(P) is a period ΔT_(P) based on anecho processing delay, and where 0.8≤D_(j)/D_(RG(j))≤1.2, where D_(j) isthe delay D_(j) unique to the each range gate RG_(j) and D_(RG(j)) isthe associated D_(RG(j)) for the each range gate RG_(j).
 5. The methodof claim 4 further comprising providing the demodulated subcode Θ_(R) tothe plurality of range gates RG_(j) over the period ΔT_(P).
 6. Themethod of claim 5 where correlating the updated polyphase sequence usingthe set of polyphase subcodes having N number of members comprisescorrelating the updated polyphase sequence using a matched filtercomprising a reference register, where the reference register comprisesthe set of polyphase subcodes having N number of members used by thepolyphase subcode generator, thereby processing the demodulated subcodeΘ_(R).
 7. The method of claim 5 where generating the phase conversionparameter (ϕ_(i)−Θ_(i)) using the random subcode Θ_(i) and the polyphasesubcode ϕ_(i) comprises performing operations equivalent to(ϕ_(i)−Θ_(i))=ƒ₁ (ϕ_(i),Θ_(i)) where ƒ₁ is a mathematical function overat least some portion of a domain comprising ϕ_(i) and Θ_(i), and where(ϕ_(i)−Θ_(i)) is the phase conversion parameter (ϕ_(i)−Θ_(i)), ϕ_(i) isthe polyphase subcode ϕ_(i), and Θ_(i) is the random subcode Θ_(i). 8.The method of claim 7 where generating the echo subcode ϕ_(R) byconverting the demodulated subcode Θ_(R) using the most recent phaseconversion parameter (ϕ_(k)−Θ_(k)) comprises performing operationsequivalent to ϕ_(R)=ƒ₂ ((ϕ_(k)−Θ_(k)), Θ_(R)), where ƒ₂ is amathematical function over at least some portion of a domain comprising(ϕ_(k)−Θ_(k)) and Θ_(R) and where when 0.8≤Θ_(i)/Θ_(R)≤1.2 and0.8≤(ϕ_(i)−Θ_(i))/(ϕ_(k)−Θ_(k))≤1.2, then 0.8≤ϕ_(i)/ϕ_(R)≤1.2, whereΘ_(R) is the demodulated subcode Θ_(R), (ϕ_(k)−Θ_(k)) is the most recentphase conversion parameter (ϕ_(k)−Θ_(k)), and ϕ_(R) is the echo subcodeΘ_(R).
 9. The method of claim 5 where the continuous wavephase-modulated random radar signal comprises a plurality of randomsubcodes Θ_(i) where the plurality of random subcodes Θ_(i) defines aplurality of phases over a time period T, and each phase comprising theplurality of phases satisfies a relationship 0.8≤p/x_(PDF)≤1.2, where pis the each phase comprising the plurality of phases and X_(PDF) is apoint on a probability density function (μ,σ²).
 10. A system fortransmitting a randomly modulated subcode and processing echo returns: atransmitting system comprising: a random waveform generator receiving arandom noise signal and generating a random subcode Θ_(i), where therandom subcode Θ_(i) has a subpulse width τ where τ is a measure oftime; a polyphase subcode generator producing a polyphase subcode ϕ_(i)corresponding to the random subcode Θ_(i) where the polyphase subcodeϕ_(i) is a member of a set of polyphase subcodes having N number ofmembers; an antenna system transmitting a modulated subcode Θ′_(i) at atime t_(i), where the modulated subcode Θ′_(i) is an electromagneticsignal having a frequency and having a phase over the subpulse width τdependent on the random subcode Θ_(i), thereby transmitting the randomlymodulated subcode; and a corrections generator performing stepscomprising: receiving the random subcode Θ_(i) from the random waveformgenerator; receiving the polyphase subcode ϕ_(i) from the polyphasesubcode generator; and generating a phase conversion parameter(ϕ_(i)−Θ_(i)) using the random subcode Θ_(i) and the polyphase subcodeϕ_(i) and providing the phase conversion parameter (ϕ_(i)−Θ_(i)) to aplurality of range gates comprising two or more range gates RG_(j),where j is an integer unique to each range gate RG_(j) and j is greaterthan or equal to 1, by providing the phase conversion parameter(ϕ_(i)−Θ_(i)) to the each range gate RG_(j) following a delay D_(j)after transmission of the modulated subcode Θ′_(i) from the antennasystem, where the delay D_(j) is unique to the each range gate RG_(j);the antenna system receiving an echo return of the modulated subcodeΘ′_(i) transmitted by the antenna system; a demodulator receiving theecho return and demodulating the echo return to produce a demodulatedsubcode Θ_(R), and providing the demodulated subcode Θ_(R) to theplurality of range gates; the each range gate RG_(j) receiving thedemodulated subcode Θ_(R) and receiving the phase conversion parameter(ϕ_(i)−Θ_(i)) following the delay D_(j), and the each range gate RG_(j)processing the demodulated subcode Θ_(R), thereby processing echoreturns.
 11. The system of claim 10 further comprising the demodulatorreceiving the echo return and demodulating the echo return to produce ademodulated subcode Θ_(R) and providing the demodulated subcode Θ_(R) tothe plurality of range gates over a period ΔT_(P).
 12. The system ofclaim 11 further comprising the corrections generator providing thephase conversion parameter (ϕ_(i)−Θ_(i)) to the each range gate RG_(j)using an associated D_(RG(j)) for the each range gate RG_(j), where theassociated D_(RG(j)) for the each range gate RG_(j) is equal to2τ(j)+ΔT_(P), and where 0.8≤D_(j)/D_(RG(j))≤1.2, where D_(j) is thedelay D_(j) unique to the each range gate RG_(j) and D_(RG(j)) is theassociated D_(RG(j)) for the each range gate RG_(j).
 13. The system ofclaim 12 further comprising the each range gate RG_(j) processing thedemodulated subcode Θ_(R) by: generating an echo subcode ϕ_(R) byconverting the demodulated subcode Θ_(R) using the phase conversionparameter (ϕ_(i)−Θ_(i)) received from the corrections generatorfollowing the delay D_(j); modifying a polyphase sequence comprising astring of subcodes by adding the echo subcode ϕ_(R) to the polyphasesequence, thereby generating an updated polyphase sequence; andcorrelating the updated polyphase sequence using the set of polyphasesubcodes having N number of members used by the polyphase subcodegenerator, thereby processing the demodulated subcode Θ_(R).
 14. Thesystem of claim 13 further comprising: the corrections generatorgenerating the phase conversion parameter (ϕ_(i)−Θ_(i)) by performingoperations equivalent to (ϕ_(i)−Θ_(i))=ƒ₁ (ϕ_(i), Θ_(i)) where ƒ₁ is amathematical function over at least some portion of a domain comprisingϕ_(i) and Θ_(i), and where (Θ_(i)−Θ_(i)) is the phase conversionparameter (ϕ_(i)−Θ_(i)), ϕ_(i) is the polyphase subcode Θ_(i), and Θ_(i)is the random subcode Θ_(i); the each range gate RG_(j) generating theecho subcode ϕ_(R) by performing operations equivalent to ϕ_(R)=ƒ₂((ϕ_(k)−Θ_(k)), Θ_(R)), where ƒ₂ is a mathematical function over atleast some portion of a domain comprising (ϕ_(k)−Θ_(k)) and Θ_(R) andwhere when 0.8≤Θ_(i)/Θ_(R)≤1.2 and 0.8≤(ϕ_(i)−Θ_(i))/(ϕ_(k)−Θ_(k))≤1.2,then 0.8≤ϕ_(i)/ϕ_(R)≤1.2, where Θ_(R) is the demodulated subcode Θ_(R),(ϕ_(k)−Θ_(k)) is the most recent phase conversion parameter(ϕ_(k)−Θ_(k)), and ϕ_(R) is the echo subcode ϕ_(R).
 15. The system ofclaim 14 further comprising: the random waveform generator using aplurality of random noise signals and generating a plurality of randomsubcodes Θ_(i), where the plurality of random subcodes Θ_(i) defines aplurality of phases over a time period T, and where each phasecomprising the plurality of phases satisfies a relationship0.8≤p/x_(PDF)≤1.2, where p is the each phase comprising the plurality ofphases and x_(PDF) is a point on a probability density function (μ,σ²),and; the antenna system transmitting a plurality of modulated subcodesΘ′_(i), where every modulated subcode Θ′_(i) in the plurality ofmodulated subcodes Θ′_(i) is an electromagnetic signal having afrequency and having a phase over the subpulse width τ dependent on oneof the random subcodes Θ_(i), comprising the plurality of randomsubcodes Θ_(i).
 16. A Continuous Wave Radar Apparatus comprising: one ormore digital processors programmed to generate a plurality of randomsubcodes, communicate a plurality of phase conversion parameters, andprocess echo returns by performing steps comprising: I) generating arandom subcode Θ_(i); II) producing a polyphase subcode ϕ_(i)corresponding to the random subcode Θ_(i) where the polyphase subcodeϕ_(i) is a member of a set of polyphase subcodes having N number ofmembers; III) generating a phase conversion parameter (ϕ_(i)−Θ_(i))using the random subcode Θ_(i) and the polyphase subcode ϕ_(i) andproviding the phase conversion parameter (ϕ_(i)−Θ_(i)) to a plurality ofrange gates comprising two or more range gates RG_(j), where j is aninteger unique to each range gate RG_(j) and j is greater than or equalto 1, by providing the phase conversion parameter (ϕ_(i)−Θ_(i)) to theeach range gate RG_(j) following a delay D_(j) after a transmission timet_(i), where the delay D_(j) is unique to the each range gate RG_(j);IV) generating a modulated subcode Θ′_(i) having a phase over a subpulsewidth τ, where τ is a measure of time, and where the phase is based onthe random subcode Θ_(i); V) communicating the modulated subcode Θ′_(i)to an antenna system; VI) receiving a time signal and using the timesignal as the transmission time t_(i); IV) repeating step I), step II),and step III), step IV), step V), and step VI), thereby generating theplurality of random subcodes and communicating the plurality of phaseconversion parameters; IIV) producing and providing a demodulatedsubcode Θ_(R) by: IIV)A) receiving an echo return from the antennasystem; IIV)B) demodulating the echo return and producing a demodulatedsubcode Θ_(R); and IIV)C) providing the demodulated subcode Θ_(R) toeach range gate RG_(j) comprising the plurality of range gates RG_(j);and IIIV) processing the demodulated subcode Θ_(R) by directing the eachrange gate to perform steps comprising: IIIV)A) receiving thedemodulated subcode Θ_(R); IIIV)B) identifying a most recent phaseconversion parameter (ϕ_(k)−Θ_(k)), where the most recent phaseconversion parameter (ϕ_(k)−Θ_(k)) is the phase conversion parameter(ϕ_(i)−Θ_(i)) most recently provided to the each range gate RG_(j);IIIV)C) generating an echo subcode ϕ_(R) by converting the demodulatedsubcode Θ_(R) using the most recent phase conversion parameter(ϕ_(k)−Θ_(k)); IIIV)D) modifying a polyphase sequence comprising astring of subcodes by adding the echo subcode ϕ_(R) to the polyphasesequence, thereby generating an updated polyphase sequence; and IIIV)E)correlating the updated polyphase sequence using the set of polyphasesubcodes having N number of members used by the polyphase subcodegenerator, thereby processing the demodulated subcode Θ_(R), therebyprocessing echo returns; the antenna system in data communication withthe one or more digital processors and the antenna system configured toreceive the modulated subcode Θ′_(i) and transmit the modulated subcodeΘ′_(i), in response to a transmit signal, and the antenna systemconfigured to provide the echo return to the one or more digitalprocessors; and a timing circuit in data communication with the antennasystem and the one or more digital processors and configured to providethe time signal to the one or more digital processors and the transmitsignal to the antenna system.
 17. The Continuous Wave Radar Apparatus ofclaim 16 where the one or more digital processors are further programmedto perform steps comprising: performing step IIV)A, step IIV)B), andstep IIV)C over a period of time ΔT_(P); and providing the phaseconversion parameter (ϕ_(i)−Θ_(i)) to the each range gate RG_(j) usingan associated D_(RG(j)), for the each range gate RG_(j), where theassociated D_(RG(j)), for the each range gate RG_(j) is equal to2τ(j)+ΔT_(P) and where 0.8≤D_(j)/D_(RG(j))≤1.2, where D_(j) is the delayD_(j) unique to the each range gate RG_(j), D_(RG(j)), is the associatedD_(RG(j)), for the each range gate RG_(j), and ΔT_(P) is the period oftime ΔT_(P).
 18. The Continuous Wave Radar Apparatus of claim 17 wherethe one or more digital processors are further programmed to direct theeach range gate to correlate the updated polyphase sequence by using amatched filter comprising a reference register, where the referenceregister comprises the set of polyphase subcodes having N number ofmembers used by the polyphase subcode generator.
 19. The Continuous WaveRadar Apparatus of claim 18 where the one or more digital processors arefurther programmed to: generate the phase conversion parameter(ϕ_(i)−Θ_(i)) by performing operations equivalent to (ϕ_(i)−Θ_(i))=ƒ₁(ϕ_(i),Θ_(i)) where ƒ₁ is a mathematical function over at least someportion of a domain comprising ϕ_(i) and Θ_(i), and where (ϕ_(i)−Θ_(i))is the phase conversion parameter (ϕ_(i)−Θ_(i)), ϕ_(i) is the polyphasesubcode ϕ_(i), and Θ_(i) is the random subcode Θ_(i); and direct theeach range gate RG_(j) to generate the echo subcode ϕ_(R) by performingoperations equivalent to ϕ_(R)=ƒ₂ ((ϕ_(k)−Θ_(k)), Θ_(R)), where ƒ₂ is amathematical function over at least some portion of a domain comprising(ϕ_(k)−Θ_(k)) and Θ_(R) and where when 0.8≤Θ_(i)/Θ_(R)≤1.2 and0.8≤(ϕ_(i)−Θ_(i))/(ϕ_(k)−Θ_(k))≤1.2, then 0.8≤ϕ_(i)/ϕ_(R)≤1.2, whereΘ_(R) is the demodulated subcode Θ_(R), (ϕ_(k)−Θ_(k)) is the most recentphase conversion parameter (ϕ_(k)−Θ_(k)), and ϕ_(R) is the echo subcodedϕ_(R).
 20. The Continuous Wave Radar Apparatus of claim 19 furthercomprising a noise source in data communication with the one or moredigital processors, and the one or more digital processors programmed togenerate the random subcode Θ_(i) using the noise source.